Engineering 101

Pivotal Discovery Identifies Battery Performance Decline

Performance decline caused by repeated charge-discharge cycling in the cathodes is the bane of next-generation batteries. EVs need greater ranges, and the grid requires low-cost batteries to store intermittent clean energy.

The sodium-ion battery is a promising solution. It is attractive because of the abundance and lower cost of sodium compared to lithium. When cycled at high voltage, a sodium-ion battery can significantly increase the amount of energy stored in a given weight or volume. Yet, it has a rapid performance decline with charge-discharge cycling, a barrier to commercialization.

Researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have identified what’s behind that degradation: defects in the atomic structure that form during the steps involved in preparing the cathode material. The defects lead to a structural earthquake in the cathode and a catastrophic performance decline during battery cycling. Armed with this knowledge, battery developers will now be able to adjust synthesis.

Research data revealed that, upon rapidly dropping the temperature during material synthesis, the cathode particle surface had become less smooth and exhibited large areas indicating strain. The data also showed that a push-pull effect in these areas happens during cathode cycling, causing cracking of the cathode particles and performance decline. They published their research in a Nature Communications article entitled, ​“Native lattice strain induced structural earthquake in sodium layered oxide cathodes.”

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